Free running multivibrator circuit energizing an indicator circuit



June 1965 G. 1'. CULBERTSON 3, 3

FREE RUNNING MULTIVIBRATOR CIRCUIT ENERGIZING AN INDICATOR CIRCUIT FiledFeb. 8. 1960 INVENTOR.

Gearge .7 ('u/berfaon @WQLk HTTDRNEYJ United States Patent 3,188,623FREE RUNNING MULTIVIBRATOR CIRCUIT ENERGIZING AN INDICATOR CIRCUITGeorge T. Culbertson, Gardena, Calif., assignor, by mesne assignments,to Master Specialties Company, Gardena,

Calif., a corporation of California Filed Feb. 8, 1960, Ser. No. 7,409 4Claims. (Cl. 340331) This invention relates in general to flasherwarning devices and more particularly relates to a transistorizedflasher system.

In the modern technology of high speed aircraft and missiles, everincreasing problems of operator monitoring and warning indications areencountered. There is a constant need for a central indicator panelcapable of visually indicating the sequence of various operationsthroughout the system. Additionally, it is imperative to haveindications of faults due to abnormal changes in pressure, temperature,speed, or the like. Accordingly, one of the objects of this invention isto provide a flasher warning device which operates to give a visualindication upon the operation of a fault switch. A fault switch as usedthroughout this description is defined as a device which is located in.the input power line and which operates upon a predetermined conditionto enable the flasher device.

A further object of this invention is to provide a flasher utilizingsolid state components to increase the reliability and to minimizepreventative maintenance.

Yet another object of this invention is to provide an inexpensiveflasher which may be compactly assembled in a rugged assembly.

come apparent from .the following detailed description of a preferredembodiment thereof, reference being had to the accompanying drawingcontaining a single figure which illustrates a schematic representationof one form of the invention.

Referring now to' the figure, an. input source of direct currentpotential is applied to lines 10 and 11 being positive at terminal 12and negative at terminal 13. The application of input power iscontrolled by a fault switch 14 which is illustrated as being in thepositive line although it is apparent that it may be in the negativeline. The fault switch may be operated automatically upon the occurrenceof any predetermined condition in a wellknown manner.

A pair of injection transistors 16 and 26 have their emitter electrodes17 and 27 joined together and connected to line 10 through resistor 30.The collector electrode 18 of transistor 16 is connected to line 11through resistor 31. The collector electrode 28 of transistor 26 isconnected to line 11 through a pick-up winding 32 of an output relay andalso through a parallel path including isolating semi-conductor diode 33and resistor 34. The contacts 32a associated with winding 32 are shownin their normally de-energized position in series with an indicator lamp36 and a source of lamp voltage applied to terminals 37, 38. The baseelectrode 19 is connected between the adjustable time constant resistors40 and 41 Which have their opposite ends connected to lines 10 and 11. Acapacitor 42 joins the base 19 to the upper end of resistor 34.

In a like manner, adjustable resistors 43 and 44 join lines 10 and 11with a common connection to the base electrode 29 of transistor 26. Acapacitor 46 is connected between the base 29 and collector 18 of theopposite transistors.

In operation, one of the transistors starts to conduct when the faultswitch 14 is closed and power is applied to lines 10 and 11. Assumingfor a moment that transistor 16 starts to conduct, a complete cycle ofoperation will be described. Initially, capacitor 46 becomes slightlycharged minus to plus reading the figure from left to right. This pluspotential at the base of transistor 26 is suflicient to maintain thetransistor 26 non-conducting. With transistor 26 non-conducting, theoutput relay coil 32 is not energized and indicator lamp 36 isextinguished to indicate the off time of the flasher.

Capacitor 42 meanwhile, as transistor 16 conducts, charges through theemitter to base diode of transistor 16 and through the resistor 40 tobecome charged plus to minus, reading left to right. Capacitor 46commences to leak off its charge around the path including resistor 44,line 11 and resistor 31. A further discharge path for capacitor 46extends through resistor 43, line 10, resistor 30, and the emitter tocollector path of conducting transistor 16. It is apparent that both ofthe adjustable resistors 43 and 44 therefore control the discharge timeof capacitor 46 which, as will be seen, controls the off time of theoutput indicating lamp.

When capacitor 46 has discharged sufiiciently, transistor 26 turns onand the emitter-collector current energizes the output relay winding 32to turn the lamp 36 on. Additionally, diode 33 is poled in a forwarddirection and 'a positive potential is developed at the top of resistor34.

This positive potential is coupled to the base 19 and transistor 16turns off as a result of transistor 26 turning on. Capacitor 46 nowcharges again with a plus potential on the right with the charge paththrough the emitter to base diode of conducting transistor 26 as well asthrough resistor 43. I

Meanwhile, during conduction of transistor 26, capacitor 42 dischargesthrough a path including resistor 41, line 11 and resistor 34. A furtherdischarge path for capacitor 42 includes resistor 40, line 10,- resistor30, the emitter to collector path of transistor 26 and forward biaseddiode 33. It is also apparent that both of the adjustable resistors 40and 41 therefore control the discharge time of capacitor 42 whichcontrols the on time of the output indicating lamp. When capacitor 42discharges sufliciently, transistor 16 begins to conduct which applies apositive potential to base 29 and in turning off transistor 26 alsoturns ofI' lamp 36.

The indicator lamp on time may be varied by adjusting resistors 40 and41 while the off time may be adjusted by varying resistors 43 and 44. Itis understood that the value of capacitors 42 and 46 may be varied as anequivalent manner of controlling the oif and on time.

The circuit has been described using PNP transistors although it isunderstood by those skilled in the art that NPN transistors may besubstituted by reversing the input polarity of the power source and byreversing the direction of isolating diode 33. A proper polarity of thecoil of output relay 32 must of course also be provided.

Although the invention has been described with reference to a specificembodiment, numerous modifications are possible and it is desired tocover all modifications falling within the spirit and scope of theinvention as hereinafter claimed.

What I claim is:

1. In an electrical system for alternately energizing and de-energizingan output indicator, the. combination comprising an input direct currentpotential applied to a pair of input lines, a pair of junctiontransistors having base, emitter and collector electrodes, meansconnecting the emitter-collector circuits of said transistors acrosssaid input lines, fault switch means connected to said input lines toprovide power at a predetermined time to said transistors, a winding ofan output relay connected in the emitter-collector circuit of one ofsaid transistors, an isolating diode poled in a forward conductiondirection included in said emitter-collector circuit of the transistordriving said input relay winding, said diode permitting conductiontherethrough only when its associated transistor conducts, outputindicating means controlled by contacts of said output relay, capacitormeans cross-connected from each collector electrode to the baseelectrode of the opposite of said transistors, a pluralityflof resistorsconnected to said capacitor means from the base electrode of eachtransistor to the input lines to regulate the discharge time of saidrespective capacitor means, the charge of said capacitors alternatelymaintaining said respective transistors in a non-conducting state.

2. A flasher warning device comprising an output indicating means havinga controllable off and on time period, a direct current input potential,fault switch means selectively energizable to deliver input potential toa pair of input lines, means for controlling the oif and on' period ofsaid indicating means including a pair of junction transistors havingbase, emitter, and collector electrodes, means connecting theemitterelectrodes of said transistorsto one of said input lines, meansconnecting the collector electrodes to the other of said input lines, anoutput relay winding connected in the collector circuit of one of saidtransistorsecontact means associated with said output relay to controlthe energization of said indicating means, a pair of capacitorscross-connected from the collector electrode of each said transistor to,the base electrode of the opposite of said transistors, a sem-conductordiode in the collector circuit of said one of said transistors forisolating said output relay winding from a charging path of one of saidcapacitors, adjustable resistors connected from the base of eachtransistor to the input lines to provide a charge and discharge path forthe respective capacitors which are adjustable to control the'respectiveperiod of conduction and non-conduction of the respective transistors.

3. A controllable flasher electrical system comprising a pair of powerinput lines, a pair of junction transistors having emitter, collectorand base electrodes, the emitter electrodes being joined together andconnected to one of said input lines, the collector of one of saidtransistors connected to the second of said input lines, the collectorof the other of said transistors being connected in a parallel path tothe second of said input lines, one leg of said parallel path includingan output relay winding and the other leg including an isolating diodeconnected in a forward conduction direction to conduct only when itsassociated transistor conducts, capacitors cross-connected from the baseto collector circuits of opposite of said 5 transistors, adjustableresistors connected from the base of each transistor to the input linescontrolling the charge and discharge times of said capacitors to allowthe transistors to be alternately non-conductive, fault switch meansconnected in series with said input lines to controlthe input to' saidjunction transistors, and output relay contact I means in series with aflasher indicator which advises the respective on and off periods of therespective transistors. 4. A controllable flasher electrical systemcomprising a pair of power input lines, a first and second transistorhaving emitter, collector and base electrodes, the emitter'electrodes'being joined together and connected to one of 'said inputlines, the collector of the first of said transistors connected to thesecond of said input lines,the collector of the second of saidtransistors being connected in a parallel path to the second of saidinput lines, one leg of said parallel pathincluding an output relaywinding and the other leg including an isolating diode connected 7 7 Vin a forward conduction direction in series with an impedance means,said other leg having an intermediate junc tion point, a pair ofcapacitors cross-connected with one end of each connected to the baseelectrodes and the other'end connected to the collector circuits of theopposite of said transistors, one of said connections being to saidintermediate junction point to, isolate its capacitor from said outputrelay winding when the second of said transistors becomesnon-conducting, adjustable resistors connected fromthe base of eachtransistor to the input lines controlling the charge and discharge timesof said capacitors'to allowthe transistors to be alternatelynonconductive, fault switch means connected in series with said inputlines to control the'input to said transistors, and output relay contactmeans in series with a flasher indicator which advises the respective onand off periods of the respective transistors.

ReferencesCited by the Examiner UNITED STATES PATENTS 50 DAVID J.GALVIN, Primary'Examinr.

' ARTHUR GAUSS, GEORGE N. WESTBY, Examiners.

1. IN AN ELECTRICAL SYSTEM FOR ALTERNATELY ENERGIZING AND DE-ENERGIZINGAN OUTPUT INDICATOR, THE COMBINATION COMPRISING AN INPUT DIRECT CURRENTPOTENTIAL APPLIED TO A PAIR OF INPUT LINES, A PAIR OF JUNCTIONTRANSISTORS HAVING BASE, EMITTER AND COLLECTOR ELECTRODES, MEANSCONNECTING THE EMITTER-COLLECTOR CIRCUITS OF SAID TRANSISTORS ACROSSSAID INPUT LINES, FAULT SWITCH MEANS CONNECTED TO SAID INPUT LINES TOPROVIDE POWER AT A PREDETERMINED TIME TO SAID TRANSISTORS, A WINDING OFAN OUTPUT RELAY CONNECTED IN THE EMITTER-COLLECTOR CIRCUIT OF ONE OFSAID TRANSISTORS, AN ISOLATING DIODE POLED IN A FORWARD CONDUCTIONDIRECTION INCLUDED IN SAID EMITTER-COLLECTOR CIRCUIT OF THE TRANSISTORDRIVING SAID INPUT RELAY WINDING, SAID DIODE PERMITTING CONDUCTIONTHERETHROUGH ONLY WHEN ITS ASSOCIATED TRANSISTOR CONDUCTS, OUTPUTINDICATING MEANS CONTROLLED BY CONTACTS OF SAID OUTPUT RELAY, CAPACITORMEANS CROSS-CONNECTED FROM EACH COLLECTOR ELECTRODE TO THE BASEELECTRODE OF THE OPPOSITE OF SAID TRANSISTORS, A PLURALITY OF RESISTORS